Spread Spectrum Signal Detection Using Multiple Spreading Code Chips for Delay Compensation

This application is a continuation application of U.S. Appl. No. 19/261,810, filed on July 07, 2025, which is a continuation application of U.S. Appl. No. 18/095,499, filed on January 10, 2023, which claims priority to U.S. Prov. Appl. No. 63/298,091, filed on January 10, 2022, all entitled CONCEALED SPREAD SYMBOL COMMUNICATION, by Darren Robert Reis, et al., the contents of which are incorporated herein by reference.

The present disclosure relates generally to wireless communication systems, and, more particularly, to concealed spread symbol communication.

Aside from the risk of an adversary being able to eavesdrop on a communication channel and decipher confidential communication, there is an inherent risk of the adversary being able to detect that communication is taking place. This is risk is especially large with personnel or devices whose location should be kept secret such as soldiers behind enemy lines or covert sensors.

To reduce the chance of being detected, people can, and usually do, use communication equipment that transmit at a very low power. Spread spectrum is commonly used to spread the transmission power over a large spectrum resulting in a very low power density footprint at any specific frequency. Using spread spectrum, the power density at any given frequency can be reduced to be lower than the power of thermal noise making it non-obvious that there is any active communication at any given frequency. Communication using frequency spreading provides also the additional benefit wherein jamming of the communication by transmitting powerful signal in a specific frequency may be easily overcome.

Still, spread spectrum communications do not completely prevent an adversary from detecting that communication takes place. Since the spreading codes are well known, an adversary may be listening for transmissions and processing the received signals with multiple spreading codes. When the adversary guesses the right spreading code, the adversary can detect the transmission as well as the location of the transmitter.

According to one or more of the embodiments herein, systems and techniques are provided for concealed spread symbol communication. In particular, a system in accordance with the techniques herein relates to concealing communication (a reduced risk of being detected), particularly messages over satellites communication channels. The techniques herein provide additional message concealment by using a randomly variable sequence of spreading chips. The techniques also ensure that the randomized chip sequences used by the user equipment and by the ground station are synchronized.

Other embodiments of the present disclosure may be discussed in the detailed description below, and the summary above is not meant to be limiting to the scope of the invention herein.

As noted above, it is often the case that wireless communication needs to be kept confidential (undecipherable), as well as covert (undetected). As also noted above, although spread spectrum is commonly used produce a very low power density footprint across a range of frequencies, spread spectrum communications do not completely prevent an adversary from detecting the communication or the location of the transmitter.

The techniques herein, therefore, provide for concealed spread symbol communication that better conceals the communication transmitters, making it more difficult for an adversary to detect that any communication takes place.

Notably, one of the most used spread spectrum schemes is the orthogonal variable spreading factor (OVSF). Using this method, before each signal is transmitted, the signal is spread over a wide spectrum range through the use of a spreading code also known as a “chip”. The spreading is done by multiplying each one of the communication symbols by the chip. To facilitate communication by multiple users, each user is given a specific spreading code out of a set of mutually orthogonal spreading codes (chips).

1 FIG. 100 110 110 120 120 110 110 a h a h a h is an example illustrationthat provides a pictorial description of orthogonal spreading codes of length eight. Codesthroughcan get the values of either 1 or -1 in each one of the eight timeslotsthrough. The orthogonality property can be observed by multiplying any two of the spreading codesthroughvalues in each corresponding timeslots and summing the results. On the other hand, multiplying any chip by itself and summing up the results yields an integer equivalent to the length (number of timeslots the chip occupies) of the chip.

1 FIG. Code division multiple access (CDMA) communication assigns orthogonal chips such as those shown into various users. Each user is assigned a unique spreading code. Because the assigned chips are orthogonal, transmission from any user, who uses a first chip, once it is multiplied by a chip assigned to other users results in zero power at the receiver. The receiver demodulates a signal from any user by multiplying the received signal by the spreading code associated with the desired user. For the desired user, multiplying the received signal by the respective chip results in the original signal. On the other hand, multiplying the received signal from any other user by the chip associated with the desired user, results in zero due to the orthogonality property of the signals.

2 FIG. 200 210 220 250 250 220 230 211 221 231 251 261 260 270 210 230 a n a n illustrates an example of a communication environmentin the presence of an eavesdropping adversary (e.g., drone, satellite, etc.). Users may use user equipment(e.g., terminal, mobile device, “SatCom” device, etc.) to establish satellite communication via satelliteto communicate with intended users (user equipment, or “UEs”)through. Communication satelliteand ground stationuse communication links,,,-, andto provide communication links for the communication infrastructure. Encryption serverperforms encryption and decryption services on the transmitted and received messages. Chip synchronization serverensures that the receivers and transmitters of the mobile deviceand ground stationare kept in sync as explained in greater detail below.

225 226 280 225 226 210 Adversary satelliteand adversary droneillustratively fly above terrainwith the goal of detecting radio transmissions and determining the location of such transmission if any. Specifically, adversary satelliteand adversary droneattempt to detect the transmission from mobile deviceand determine the location from which the transmission originates.

225 226 As explained above, the fact that mobile device uses spread spectrum reduces the radio energy density of the transmitted signal. However, if the adversary satelliteand/or the adversary dronemanages to guess the spreading code (chip) used by the mobile device, it would be able to detect the transmitted signal and determine the location from which transmission takes place.

To reduce the risk of detection of the transmitting mobile device a system, the techniques in accordance with the embodiments herein utilize a different spreading code for each one of the symbols it transmits. As such, even if the adversary drone or satellite manages to guess one of the chips used, they would be able to demodulate at most only a single symbol. Given the need for detecting also the phase and timing of the signal, the probability of actually identifying the symbol is greatly reduced.

Existing methods for radio transmission concealment use longer spreading codes. However even a longer spreading code can be guessed and once found compromise the fact that radio transmission took place, including the location from where transmission took place.

In contrast, a system according to the techniques herein utilizes a dynamic time varying spreading code which is much more difficult to guess by a trial and error method.

3 4 FIGS.- illustrate an example operation of a system with a dynamically variable spread code.

3 FIG. 2 FIG. 300 300 240 in particular, is a drawing of an example ground station apparatus, e.g., dynamic random spreading code synchronization module, in accordance with an example embodiment herein. In some embodiments, the dynamic random spreading code synchronization module apparatusis part of a server attached to networkshown in.

300 330 306 308 310 312 303 309 330 340 220 240 2 FIG. 2 FIG. Ground station apparatus(e.g., one illustrative “beaconing device” herein, though other types of beaconing devices may be used with the techniques herein) includes a communications interface, a processor, an output device, e.g., display, printer, etc., an input device, e.g., keyboard, keypad, touch screen, mouse, etc., a memoryand an assembly of components, e.g., assembly of hardware components, e.g., assembly of circuits, coupled together via a busover which the various elements may interchange data and information. Network communications interfaceand radio communication interfacefacilitate external communication via satellite such as satelliteofand communication network such as networkof.

330 332 250 334 300 250 2 FIG. 2 FIG. Network communications interfaceincludes a receivervia which the ground station apparatus can receive data and information, e.g., including communication information from user devices e.g., devicesof, and a transmitter, via which the ground station apparatuscan send data and information, e.g., message exchange with UEsof, etc.

340 342 210 344 300 210 2 FIG. 2 FIG. Radio communications interfaceincludes a receivervia which the ground station apparatus can receive data and information, e.g., including communication information from user devices e.g., devicesof, and a transmitter, via which the ground station apparatuscan send data and information, e.g., message exchange with UEof, etc.

312 314 317 350 314 318 320 318 210 320 303 260 Memoryincludes routines, data/information, and chip table. Routinesinclude assembly of components, e.g., an assembly of software components, and random number generator. In accordance with one embodiment, the software componentsinclude also a module that generates a beacon signal that is broadcasted by the ground station to all of the UEs. In accordance with a specific embodiment, the beacon signal includes a random number generated by the random number generator. In accordance with another embodiment, the random number generator is a module of the HW assembly. In accordance with yet another embodiment the random number generator and/or the beacon generation module are modules of a network attached server.

210 210 2 FIG. 2 FIG. In either case the ground station broadcasts a random number to all of the mobile devices such as UEsof(only one UE is shown). As explained below in greater detail, the random number that is included in the beacon transmitted from the ground station towards the mobile devices is changed periodically, e.g., every few seconds, every minute, or whenever the ground station detects communication from a new mobile device such as deviceof.

317 322 321 323 324 321 320 324 210 210 2 FIG. 2 FIG. Data informationincludes a configuration dataentered by the system administration, current random number storage(maintains the random number that is currently transmitted), previous random number storage(the previous randomly generated number which was used previously), and current random number seed storage(described below). Current random number storagemaintains the random number which is generated by the random number generatorbased on the random number seed stored in current random number seed storage. As explained below in greater detail, the mobile UE such as UEofuse the broadcasted random number in order to select a specific chip with which it modulates symbols as part of their spread spectrum modulation. The ground station continuously listens to transmissions from any potential transmitter such as UEofand attempts to demodulate the signal using the chip it knows that the UE would use upon receiving the random number it is currently broadcasting.

210 220 324 323 2 FIG. However, due to the delay associated in the communication between the ground station and the mobile device such as device(e.g., from the round trip traversal via a satellitein), there could be a case wherein the ground station switches to broadcast a new seed random number as part of its beacon signal and shortly after that it receives a signal that was transmitted by the UE and modulated by a chip associated with the previous random number. Therefore, the ground station must listen to the received signals not only by using a chip associated with the current random numberbut also using a chip associated with the previous random number.

312 350 352 320 354 352 The memoryincludes also chip tablewhich associates chips with specific random numbers. Columnprovides entries of random numbers that can be generated by the random number generator such as random number generator. Columnprovides a unique chip ID for each one of the random numbers in column.

342 350 324 321 350 323 As explained above, when ground station broadcasts a specific random number seed, which corresponds to a specific random number, as part of its beacon signal, the radio receiver of the ground station, e.g., receiver, uses the chip associated by tablewith the current random number seed stored in memory(or associated accordingly with the associated random number stored in memory storage). Additionally, to compensate for the communication delay of the satellite communication system, the receiver is instrumented to continuously monitor the received signal and also attempt to decode it using a chip associated by tablewith the previous random number stored in memory module.

It should be noted that for sake of simplicity of explanation the figure illustrates only a single previous random number and as such only association with a single chip. In operation, however, the system may, and often does, store multiple previous random numbers and their associated chips resulting in a longer chip signal that facilitates the detection and de-spreading of the received signal.

317 325 326 The data informationalso includes mobile radio UE synchronization tracking table including columnsand. As explained in greater detail below, the mobile device starts transiting information modulated by a specific chip associated with a random number it receives via the broadcasted beacon. Then, according to an agreed upon rule (which can be, and often is) configured by the system administrator, after transmitting n symbols (e.g., n=1, 2, etc.) modulated with a first chip, it uses its own random number generator and generates a new random number. The new random number is associated with a new spread spectrum chip that the UE uses to transmit the next symbol.

324 323 325 326 Upon successfully de-spreading a signal from a UE using either a chip associated with current random numberor by the previous random number, the ground station stores the ID of the UE from which it received a message in a table and specifically in columnof the table. Accordingly, the associated chip ID used for de-spreading the signal from that specific UE is stored in columnof the table.

342 The ground station follows the same rule of updating the chip used for de-spreading and after de-spreading n symbols (e.g., n=1, 2, 3, …) with the first chip, it uses the first chip ID associated with that UE to generate the next random number in a manner similar to (e.g., identical to) the way the mobile radio device updates its random number and the associated chip ID. As such, the receiveris synchronized with the random chip that each UE is using at any time. This allows a receiver of the ground station to de-spread and to receive information from UEs that continuously change in a random way the chip they use. On the other hand, an adversary that does not have access to the information would not be able to recreate this random sequence of chips and as such would fail to detect the signal which is transmitted at or below the noise level, e.g., 5 db below the noise level.

210 325 326 2 FIG. The ground station and the radio mobile device. e.g., UEof, may get out of sync in case. This could happen if due to noise or jamming the ground station fails to decode one of the information symbols transmitted by the UE or when the UE fails to decode the acknowledgment send by the ground station. In either case, when the UE determines a potential breakdown in communication it reverts back to listening to the beacon transmitted from the ground station and picking up the current random number from the beacon signal. Since the receiver of the ground station always listens to received signals and attempts to demodulate them (de-spread them) with chips associated with either current random number or the previous random number, the random ground station and the UE re-establish a synchronized random number and proceed using it as described above using the UE specific entries in the table with columnsand.

4 FIG. 400 is a drawing of an example user equipment apparatus, e.g., a mobile radio communication device that uses dynamic random spreading code synchronization in accordance with an example embodiment.

400 430 406 408 410 412 403 409 430 220 240 2 FIG. 2 FIG. User equipment apparatusincludes a radio communications interface, a processor, an output device, e.g., display, printer, speaker, etc., an input device, e.g., keyboard, keypad, touch screen, mouse, microphone, etc., a memoryand an assembly of components, e.g., assembly of hardware components, e.g., assembly of circuits, coupled together via a busover which the various elements may interchange data and information. Radio communications interfacefacilitate external communication via satellite such as satelliteofand communication network such as networkof.

430 432 250 230 430 434 400 230 250 2 FIG. 2 FIG. 2 FIG. Radio communications interfaceincludes a receivervia which the user equipment apparatus can receive data and information, e.g., including communication information from user devices e.g., devicesof, via ground station, e.g., ground stationof. Communications interfaceincludes also a transmitter, via which user equipment apparatuscan send data and information, e.g., message exchange with ground stationand UEsof, etc.

412 414 417 450 414 418 420 418 230 424 2 FIG. Memoryincludes routines, data/information, and chip table. Routinesinclude assembly of components, e.g., an assembly of software components, and random number generator. In accordance with one embodiment the software componentsalso includes a module that analyzes the beacon signal that is broadcasted by the ground station, e.g., such as ground stationof. As part of the processing the system determines the random number transmitted by ground station and stores it in current random seed storage space.

424 423 450 454 450 When the UE is about to send the first symbol of a message, it uses the current random number seedto generate an associated random number. The random number is used as an entry into the chip tableand selects the associated chip from row. As soon as the current random number is used, the random number generator is invoked to generate the next random number. The next random number is used to pick up the next chip from the chip table, and the next chip is used to transmit the next symbol of the message.

350 450 300 400 In accordance with another embodiment, the random number is updated in accordance to the same rule that governs the random number updates in the ground station. Thus, both the ground station and the user equipment maintain the same random number which is shared only by these devices. Consequently, both devices which use the same chip table mapping tableandresulting in both devices using the same chip. This synchronization guarantees that the ground stationand the UEcan de-spread (demodulate) the signal send by the UE to the ground station as well as the signal send by the ground station to the UE.

On the other hand, adversaries that attempt to detect the signal which is send at a frequency power density below noise level would not be able to reconstruct the right sequence of chips and therefore would not be able to de-spread the signal, resulting in concealment of radio being transmitted by the UE.

230 400 2 FIG. The ground station, e.g., ground stationof, and the radio mobile device, may get out of sync in certain cases. This could happen if due to noise or jamming the ground station fails to decode one of the information symbols transmitted by the UE or when the UE fails to decode the acknowledgment send by the ground station. In either case when the UE determines a potential breakdown in communication it reverts back to listening to the beacon transmitted from the ground station and picking up the current random number seed from the beacon signal. As explained above, the seed is used as an input for the random signal generator which produces a random number identical to a number which is in the ground station. This number is used by the UE as an entry into the chip table resulting in the UE obtaining the same chip used in the ground station receiver. This would facilitate establishment of a new connection between the UE and the ground station. The operation would continue normally per explanation above.

5 5 FIGS.A-B 500 500 505 510 a b provide an example procedure (flowchartsand) of ground station beacon transmission and message reception. The process starts at operationand proceeds to operationwhere the ground station selects a random number seed. For example the number can be obtained by taking a specific counter number in the software, checking the specific time a SW module was reset, etc.

512 The process continues to operationwhere the seed number is added into a broadcast message and transmitted to all UEs as part of a beacon signal transmitted via the satellite towards the UEs.

514 320 3 FIG. In operationthe ground station generates random numbers based on the seed number, e.g., by a random number generator such as random number generatorof.

516 350 3 FIG. The process proceeds to operationwhere the method uses a chip table such as chip tableofto generate a sequence of associated chips (identifying chips associated with the random numbers).

518 520 210 2 FIG. The process proceeds to operationwhere the sequence of chips is used to de-spread the received signal. In operationthe method examines the de-spread signal and determines whether the received signal contains symbols associated with a message transmitted from one of the UEs such as UEof.

520 522 522 512 If operationdetermines that the ground station receiver did not detect any symbols sent from any UE, the process proceeds to operation. In operationthe method utilizes a preprogramed or a preconfigured rule for updating the seed of the random number generator. For example, the update may occur every second, minute, hour, every day or at any random period. The updated (or old) seed number is communicated to operationwherein the new (or old) seed number is broadcasted to the UEs.

520 210 525 530 500 530 532 534 2 FIG. 5 FIG.B b However if operationsdetects a symbol (or symbols) as part of a message sent from a UE such as UEof, the process proceeds via a connector Ato operationin flowchartof. Operationexamines whether the detected symbol signifies that the end of the message has been detected. If the end of the message has been detected the method proceeds to operationwherein the ground station sends an acknowledgement message to the UE, and the method proceeds to operation.

530 534 However, if operationdetermines that the detected symbol does not signify that an end of a message has been detected, the method proceeds directly to operationwhere a new random number is generated.

535 350 516 3 FIG. 5 FIG.A In either case, the method loops back via connection step Band uses the chip table such as chip tableofto generate a new set of chips for detecting the next message from the UE in operationof.

Transmissions of messages from the ground station which do not need to be concealed can use a single predetermined chip known to both the ground station and the UEs. Alternatively, the ground station may also use a time varying chip sequence as described below.

6 6 FIGS.A-B 5 FIG.A 600 600 605 610 510 a b provide an example procedure (flowchartsand) of sending a message from the ground station to a UE. The process starts at operationand proceeds to operationwhere the ground station selects a random number seed. For example the number can be obtained by taking a specific counter number in the software, checking the specific time a SW module was reset, etc. This step is identical to stepof.

612 512 5 FIG.A The process continues to operationswhere the seed number is added into a broadcast message and transmitted to all UEs as part of a beacon signal transmitted via the satellite towards the UEs. By receiving the seed number UEs are able to generate the same random number as the one generated in the ground station and consequently generate the same chip sequence which is used by the ground station to spread a transmitted message. This step is the same as stepof.

614 514 320 5 FIG.A 3 FIG. In operation, which is the same as operationof, the ground station generates random numbers based on the seed number, e.g., by a random number generator such as random number generatorof.

616 516 350 5 FIG.A 3 FIG. The method proceeds to operation, which is the same as operationof, where the method uses a chip table such as chip tableofto generate a sequence of associated chips.

620 The method proceeds to stepwhere the operation determines if the ground station has a message that it needs to send to a specific UE. In accordance with one embodiment the determination that the ground station needs to transmit the message is made based on the fact that the ground station has a message for a UE in its outbound queue. In accordance with yet another embodiment the determination is based on the existence of a message in the outbound queue as well as a request from the UE to transmit to it any message that is intended to it.

622 522 320 612 5 FIG.A 3 FIG. If the operation determines that there is no message in the outbound queue, the method proceeds to operation, which is identical to operationof, where the operational rules determine whether the random number should be modified, and if affirmative, modify the random number using the random number generatorabove of. The method then loops back to operationwhere the ground station continues to send the beacon signal (including the updated seed number for the random generator), and de-spread the received signal in an attempt to detect incoming messages – if any.

620 625 630 600 b 6 FIG.B However if operationdetermines that there is a message to be sent to a UE, the method proceeds via a connection step Ato operationin flowchartof.

630 614 320 632 2 FIG. Operationspreads the symbols of the message using a sequence of chips associated with the sequence of random numbers derived in stepusing the random number generatorof. The method proceeds to operationwhere the spread spectrum message is transmitted.

634 632 In operationthe ground station awaits for a predetermined time to receive an acknowledgement from the UE that it has received the message. If an acknowledgement message has not been received within a predetermined threshold time, the method loops back to stepand retransmits the message.

634 636 320 3 FIG. However if operationdetermines that an Ack message has been received, the method proceeds to operationwhere the operation generates the next random number, e.g., using the random number generatorof.

640 616 6 FIG.A The method then loops back via connector step Bto operationinwhere the next chip (or chip-set) to be used for communication with said UE is determined.

7 7 FIGS.A-B 700 700 a b provide an example procedure (flowchartsand) of process by which UE receives a message from the ground station via a satellite. It should be noted that while the process below described a flow wherein the ground station transmits (via a satellite) a spread spectrum signal that uses a randomly variable chip sequence, this operation is optional as the location of satellites is well known and as such the satellite may not need to reduce its radio signature. Rather, the satellite may use a specific not randomly variable, spreading chip.

705 710 The process starts at operationand proceeds to operationwhere the UE receives a random number seed broadcasted by a satellite from a ground station.

712 716 714 The process continues to operationswhere operation determines whether the seed number is a new seed or the same as received from the previous broadcast message. If the operation determines that the seed number did not change, the flow proceeds directly to operation. However if the operation determines that the seed number obtained from the current beacon message is different from the previous seed number, e.g., sent over the beacon signal, the method proceeds to operation.

714 420 4 FIG. In operationthe UE generates random numbers based on the seed number obtained via the received beacon message, e.g., by a random number generator such as random number generatorof.

716 450 4 FIG. The process proceeds to operationwhere the method uses a chip table such as chip tableofto generate a sequence of associated chips.

718 720 230 2 FIG. The flow proceeds to operationwhere the sequence of chips is used to de-spread the received signal. In operationthe method examines the de-spread signal and determines whether the received signal contains symbols associated with a message transmitted from one of the ground station such as ground stationof.

720 710 If operationdetermines that the UE receiver did not detect any symbols sent from the ground station, the process loops back to operation.

720 230 725 730 700 730 732 734 2 FIG. 7 FIG.B b However if operationsdetects a symbol (or symbols) as part of a message sent from a ground station such as ground stationof, the flow proceeds via a connector Ato operationof flowchartin. Operationexamines whether the detected symbol signifies that an end of the message has been detected. If an end of the message has been detected the method proceeds to operationwherein the UE sends an acknowledgement message to the ground station, and the method proceeds to operation.

730 734 736 However if operationdetermines that the detected symbol does not signify that an end of a message has been detected, the method proceeds directly to operationwhere a new random number is generated. The flow proceeds to operationwhere the new random number or in another embodiment, the new sequence of random numbers is updated.

740 716 450 7 FIG.A 4 FIG. The method loops back via connection step Bto operationinwhere the operation uses the chip table such as chip tableofto generate a new set of chips for detecting the next message from the ground station.

8 8 FIGS.A-B 800 800 a b provide an example procedure (flowchartsand) of sending a message from a UE to a ground station.

805 810 710 7 FIG.A The process starts at operationand proceeds to operationwhere the UE receives a random number seed from the ground station via a broadcast beacon message. This step is identical to stepof.

812 712 7 FIG.A The process continues to operationswhere operation determines whether the seed number is a new seed or the same as received from the previous broadcast message. This step is the same as stepof.

816 814 If the operation determines that the seed number did not change, the flow proceeds directly to operation. However if the operation determines that the seed number obtained from the current beacon message is different from the previous seed number sent via the beacon, the method proceeds to operation.

814 714 420 7 FIG.A 4 FIG. In operation, which is the same as operationof, the UE generates random numbers based on the seed number obtained via the received beacon message, e.g., by using a random number generator such as random number generatorof.

816 716 450 4 FIG. The flow proceeds to operation, which in some embodiments is the same as operation, where the method uses a chip table such as chip tableofto generate a sequence of associated chips.

818 810 The flow proceeds to operationwhere the operation determines whether the UE has a message to be sent via the satellite to the ground station. If the operation determines that there are no messages to be sent to the ground station the flow loops back to operationwhere the UE obtains a random number seed from a received beacon message.

818 825 830 800 830 816 832 b 8 FIG.B However if operationdetermines that the UE has a message that needs to be sent via a satellite to the ground station, flow proceeds via connector operation Ato operationin flowchartof. Operationuses the sequence of chips determined in stepto spread symbols of the message. Flow continues to operationwhere the message is transmitted from the UE to the ground station. Because the random numbers in the UE and the ground station are synchronized both the UE and the ground station use the same sequence of chips, this enables the ground station to de-spread and demodulate the received signal transmitted from the UE. Adversary receivers that utilize a constant single chip receiver would be able to detect at best a single symbol from a large number of symbols. As such adversary receivers would detect at best much reduced radio power resulting in greater concealment of the UE transmission.

834 834 832 Flow proceeds to operationwhere the operation awaits for a predetermined time to receive an acknowledgement from the ground station that it has received the message. If operationdetermines that an acknowledgement has not been received in the predetermined time window, e.g., five seconds, the flow loops back to operationand the message is resent.

836 However if the message has been received successfully by the ground station and a corresponding acknowledgement has been received by the UE, the flow proceeds to operationwhere a new random number(s) is generated using the random number generator of the UE.

840 816 8 FIG.A The process loops back via connector operation Bto operationinwhere the updated sequence of random numbers is used to generate a new sequence of chips to be used for spreading the symbols of the next message.

It should be noted that while certain steps within the flowcharts may be optional and the steps shown in the figures are merely examples for illustration, and certain other steps may be included or excluded as desired. Furthermore, while a particular order of the steps is shown, this ordering is merely illustrative, and any suitable arrangement of the steps may be utilized without departing from the scope of the embodiments herein. Moreover, the methods are described separately, certain steps from each procedure may be incorporated into one or more of the other methods and the various steps are not meant to be mutually exclusive.

Advantageously, the techniques herein thus provide for concealed spread symbol communication. In particular, as described above, the techniques herein provide, in one embodiment, a method for transmitting information from a device or sensor to the ground station comprising: receiving a means for synchronizing the user equipment and the ground station (e.g., receiving a random number seed from a ground station via a satellite, as described above); determining a random number based on the received seed number; determining a random sequence of chips based on the random number; spreading the symbols of the message by the random sequence of chips; and sending the spread spectrum modulated message to the ground station.

Furthermore, while the description above describes the synchronization between the user equipment and the ground station to be achieved by transmitting a random number seed via the satellite beacon signal, other synchronization methods are contemplated herein as well. In addition, while the illustrative beaconing device is shown as the ground station, other embodiments allow for the beaconing device to be a mobile terminal, thus defining the random number seed.

According to the embodiments of the present disclosure, an illustrative method herein may comprise: coordinating, by a particular device, a random number seed that is generated by a beaconing device and transmitted to one or more remote devices; generating, by the particular device, one or more random numbers based on the random number seed; determining, by the particular device, one or more spreading code chips associated with the one or more random numbers; and communicating, by the particular device, a spread spectrum message between the beaconing device and a specific remote device of the one or more remote devices based on one of either spreading or de-spreading the spread spectrum message according to the one or more spreading code chips.

In one embodiment, the beaconing device is a ground station for satellite communication, and wherein the one or more remote devices comprise mobile terminals.

In one embodiment, the random number seed is transmitted to the one or more remote devices via a broadcast message transmitted to all remote devices as part of a beacon signal from the beaconing device.

In one embodiment, the particular device is the beaconing device, and the coordinating comprises: generating the random number seed; and transmitting the random number seed to the one or more remote devices within a beacon message.

In one embodiment, the particular device is the specific remote device, and the coordinating comprises: receiving the random number seed within a beacon message from the beaconing device.

In one embodiment, identifying the one or more spreading code chips associated with the one or more random numbers is based on one of either using a chip table or a computer program.

In one embodiment, the particular device is the specific remote device, the method further comprising: determining whether the random number seed is an update from a previously received random number seed, wherein generating the one or more random numbers and identifying the one or more spreading code chips is in response to the random number seed being an update from a previously received random number seed.

In one embodiment, the one or more random numbers and the one or more spreading code chips comprise a sequence of a plurality of random numbers and a sequence of a plurality of spreading code chips, respectively.

In one embodiment, the particular device is a transmitter, and communicating comprises: spreading symbols of the spread spectrum message according to the one or more spreading code chips; and transmitting the spread spectrum message to a receiver device. In one embodiment, the method further comprises: awaiting for a predetermined time to receive an acknowledgement from the receiver device that it has received the spread spectrum message; in response to the acknowledgement not being received within the predetermined time, retransmitting the spread spectrum message; and in response to the acknowledgement being received within the predetermined time, determining one or more next random numbers and one or more next spreading code chips associated with the one or more next random numbers for a next communication.

In one embodiment, the particular device is the beaconing device, and the method further comprises: determining to initiate a communication to the specific remote device based on the beaconing device having the spread spectrum message to send to the specific remote device. In one embodiment, the method further comprises: determining to initiate the communication to the specific remote device based additionally on receiving a request from the specific remote device for the beaconing device to transmit any messages intended to the specific remote device.

In one embodiment, the particular device is a receiver, and communicating comprises: de-spreading a received signal using the one or more spreading code chips into a de-spread signal; and examining the de-spread signal to determine whether the received signal contains symbols associated with a message transmitted from a transmitter to the receiver. In one embodiment, the method further comprises: determining, in response to no symbols being detected in the de-spread signal, update for the random number seed according to an update rule. In one embodiment, the method further comprises: examining, in response to one or more symbols being detected in the de-spread signal, whether the one or more symbols signify an end of a communication; in response to the one or more symbols signifying the end of the communication, returning an acknowledgment; and in response to the one or more symbols not signifying the end of the communication; determining one or more new random numbers and one or more new spreading code chips associated with the one or more new random numbers to continue de-spreading the received signal.

In one embodiment, the one or more spreading code chips are based on an orthogonal variable spreading factor (OVSF) spread spectrum scheme.

In one embodiment, the particular device is a receiver, and communicating comprises: listening to received signals using a current spreading code chip associated with a current random number and a previous spreading code chip associated with a previous random number to account for communication delay between a transmitter and the receiver.

In one embodiment, the particular device is the specific remote device, and the method further comprises: determining a potential breakdown in communication synchronization with the beaconing device; and in response to the potential breakdown in communication synchronization, reverting back to listening for a beacon message for coordinating a current random number seed that is generated by the beaconing device and transmitted to the one or more remote devices.

Additionally, an illustrative tangible, non-transitory, computer-readable medium herein may store program instructions that cause a computer of a particular device to execute a method comprising: coordinating a random number seed that is generated by a beaconing device and transmitted to one or more remote devices; generating one or more random numbers based on the random number seed; determining one or more spreading code chips associated with the one or more random numbers; and communicating a spread spectrum message between the beaconing device and a specific remote device of the one or more remote devices based on one of either spreading or de-spreading the spread spectrum message according to the one or more spreading code chips.

Moreover, an illustrative apparatus herein may comprise: a processor configured to execute one or more processes; a communication interface; and a memory configured to store a process executable by the processor that when executed is configured to: coordinate a random number seed that is generated by a beaconing device and transmitted to one or more remote devices; generate one or more random numbers based on the random number seed; determine one or more spreading code chips associated with the one or more random numbers; and communicate a spread spectrum message between the beaconing device and a specific remote device of the one or more remote devices based on one of either spreading or de-spreading the spread spectrum message according to the one or more spreading code chips.

While there have been shown and described illustrative embodiments, it is to be understood that various other adaptations and modifications may be made within the scope of the embodiments herein. For example, the embodiments may, in fact, be used in a variety of types of wireless communication networks and/or protocols, and need not be limited to the illustrative satellite network implementation. Furthermore, while the embodiments may have been demonstrated with respect to certain communication environments, physical environments, or device form factors, and in particular satellite communication environments, other configurations may be conceived by those skilled in the art that would remain within the contemplated subject matter of the description above, including other types of wireless communication mediums aside from satellite communications.

It will also be apparent to those skilled in the art that other processor and memory types, including various computer-readable media, may be used to store and execute program instructions pertaining to the techniques described herein. Also, while the description illustrates various processes, it is expressly contemplated that various processes may be embodied as modules configured to operate in accordance with the techniques herein (e.g., according to the functionality of a similar process). Further, while the processes have been shown separately, those skilled in the art will appreciate that processes may be routines or modules within other processes.

Notably, in other embodiments, user intervention is not necessary at “user equipment” 210/250, and as such, various automated terminals, drones/UAVs, weaponry, etc., may employ the techniques herein. The use of the term “user” herein thus is not meant to be limiting to the scope of the types of devices implementing the techniques herein.

Furthermore, in the detailed description, numerous specific details are set forth in order to provide a thorough understanding of some embodiments. However, it will be understood by persons of ordinary skill in the art that some embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, units and/or circuits have not been described in detail so as not to obscure the discussion.

In particular, the foregoing description has been directed to specific embodiments. It will be apparent, however, that other variations and modifications may be made to the described embodiments, with the attainment of some or all of their advantages. For instance, it is expressly contemplated that certain components and/or elements described herein can be implemented as software being stored on a tangible (non-transitory) computer-readable medium (e.g., disks/CDs/RAM/EEPROM/etc.) having program instructions executing on a computer, hardware, firmware, or a combination thereof.

Accordingly, this description is to be taken only by way of example and not to otherwise limit the scope of the embodiments herein. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true intent and scope of the embodiments herein.